The Boeing 737 Max airliner has been grounded by regulatory agencies and airlines worldwide.

The action comes after two nearly brand-new Boeing 737 Max 8 airliners crashed within a matter of months.

The crashes, the grounding of the fleet, and the public furor make the Boeing 737 Max one of the most controversial airliners in recent memory.

Other airliners that ran into trouble include the de Havilland Comet, McDonnell Douglas DC-10, and the Airbus A320.

The US Federal Aviation Administration grounded the Boeing 737 Max airliner on Wednesday. It was the last and arguably most significant regulatory body to take action against Boeing's state-of-the-art single-aisle jet.

The enforcement action against the Boeing jet comes after two 737 Max 8 airliners crashed under strikingly similar circumstances in a matter of months.

At the heart of the controversy surrounding the 737 Max is the Maneuvering Characteristics Augmentation System (MCAS). To fit the Max's larger, more fuel-efficient engines, Boeing had to redesign the way it mounts engines on the 737. This change disrupted the plane's center of gravity and caused the Max to have a tendency to tip its nose upward during flight, increasing the likelihood of a stall. MCAS is designed to automatically counteract that tendency and point the nose of the plane downward.

On Wednesday, Boeing announced that a software update to correct the shortcomings of MCAS is incoming. Until then, all 371 Boeing 737 Max airliners already delivered to customers remain grounded.

As a result of the crashes, the grounding of the fleet, and the public furor, the Boeing 737 Max has become one of the most controversial airliners in recent memory.

But the Max isn't the first plane to run into trouble, and many have been able to overcome their problems to have successful careers.

Here's a closer look at some of the most controversial airliners in recent history:

1/

De Havilland Comet

AP

The de Havilland Comet ushered in the age of jet-powered passenger flight when it entered service in 1952.

The shiny new jet was fast, sleek, and represented the pinnacle of aviation technology. And then, one by one, Comets started falling out of the sky.

Some of the early crashes were attributed to a design flaw with the wings, which was quickly fixed.

Between summer 1953 and spring 1954, three Comets broke apart in midair. The plane was grounded by the British government in 1954.

It was eventually discovered that the plane disintegrated because of metal fatigue, which was exacerbated by the square shape of its cabin windows. The Comet was redesigned with thicker skin and oval windows before it was allowed back in service.

Unfortunately for the Comet, by that time, America's Boeing 707 and Douglas DC-8 had taken over as the airline industry's jet-powered workhorses. More than 100 Comets would be built during the 1950s and early '60s. Later versions of the Comet would continue in airliner service until the early '80s.

2/

McDonnell Douglas DC-10

AP

The three-engine McDonnell Douglas DC-10 entered service in 1971 as a smaller rival to the Boeing 747 jumbo jet. But from the beginning, the DC-10 was plagued by problems.

In 1972, American Airlines Flight 96, a nearly brand-new DC-10, had to make an emergency landing in Detroit after losing cabin pressure because the plane's cargo door blew off mid-flight. A few passengers and crew were injured, but no one was killed.

Two years later, Turkish Airlines Flight 981, another DC-10, also suffered decompression when its cargo door blew off mid-flight. Unfortunately, this time the explosive force of the air rushing out of the plane caused the cabin floor to buckle, damaging the flight controls.

All 346 passengers and crew on board the plane were killed when it nosedived into the French countryside.

The issues that plagued the DC-10 didn't stop there.

The DC-10 was grounded in 1979 after improper maintenance procedures led an engine to fall off the wing of American Airlines Flight 191 while taking off from Chicago. All 271 people on board the plane were killed, along with two others on the ground.

But the plane went on to become a workhorse for American, United, Continental, and Northwest airlines. It finally exited scheduled passenger service in 2014 and remains popular with cargo carriers such as FedEx.

3/

Airbus A320

Airbus

The Airbus A320 helped put its creator, Airbus, on the map. Since its introduction in the mid-1980s, the single-aisle jet has become the second-best-selling airliner in history, behind only the Boeing 737.

The highlight of the A320 is its advanced fly-by-wire computer-assisted control system. At the time of its debut, there was great debate over whether the industry was ready for such high levels of automation.

The concerns about human-machine interaction were further inflamed by the crash of Air France Flight 296, a demonstration flight designed to promote the capabilities of the A320 that crashed during an air show in 1988. The crash killed three of the passengers on board.

"The A320 has new features which may have inspired some overconfidence in the mind of the Captain," investigators said in their final report.

But the plane's reputation recovered in the three decades since the incident.

4/

Boeing 737 Max

Boeing

The Boeing 737 Max started flying passengers in 2017 and, for the first year and a half of its service life, it was relatively trouble-free.

But on October 28, 2018, Lion Air Flight JT610, a 2-month-old Boeing 737 Max 8, crashed shortly takeoff from Jakarta, Indonesia, killing all 189 people on board. On March 10, another nearly brand-new 737 Max 8 crashed, and once again, it was within minutes of takeoff. This time, it was Ethiopian Airlines Flight ET302, and another 157 people were killed.

Soon after the Lion Air crash, the existence of the flight-control system MCAS came to light.

Initial reports from the Lion Air investigation indicated that a faulty sensor reading may have triggered MCAS shortly after the flight took off. Observers fear that a similar thing may have happened in the March 10 Ethiopian Airlines flight.

Troublingly, pilots flying the 737 Max did not know MCAS existed until Boeing sent out a memo about it after the Lion Air crash, The Wall Street Journal reported.